1. Field of Invention
The present invention relates to a semiconductor device provided with an element which has a layer containing an organic compound over a flexible substrate, and also relates to a manufacturing method of the semiconductor device.
2. Description of the Related Art
In recent years, development has been advanced on semiconductor devices which have various functions by integrating a plurality of circuits over insulating surfaces. Moreover, development has also been advanced on semiconductor devices which can send and receive data wirelessly by providing antennas. Such semiconductor devices are referred to as wireless chips (also referred to as ID tags, IC tags, IC chips, RF (Radio Frequency) tags, wireless tags, electronic tags, or RFID (Radio Frequency Identification) tags) and have been already introduced into some markets.
Many of these semiconductor devices which have been put into practical use have circuits using semiconductor substrates made of Si or the like (such circuits are also referred to as IC (Integrated Circuit) chips) and antennas, and the IC chip includes a storage circuit (also referred to as a memory), a control circuit, and the like. In particular, by providing a storage circuit capable of storing a large amount of data, a higher-value-added semiconductor device with improved performance can be provided.
It has been required to manufacture these semiconductor devices at low cost, and development has been extensively carried out recently on elements such as transistors, memories, and solar cells using layers containing organic compounds for control circuits, storage circuits, or the like (see, for example, Reference 1: Japanese Patent Laid-Open No. 2004-47791).
Various applications of such semiconductor devices are expected, and usage of flexible plastic films is attempted in pursuit of reduction in size and weight.
Since plastic films have low heat resistance, it is necessary to decrease the highest temperature in a process. Therefore, TFTs cannot be formed using a plastic film to have as favorable electrical characteristics as those formed over a glass substrate.
Consequently, such a technique is suggested that elements formed over a glass substrate are separated from the substrate and attached to another base material such as a plastic film (see Reference 2: Japanese Patent Laid-Open No. 2003-174153).
However, in the case of separating an element which has a layer containing an organic compound by using a separation step shown in Reference 2; specifically, in the case of forming a separation layer 102 over a substrate 101, forming an insulating layer 103 over the separation layer 102, forming a thin film transistor 1111 over the insulating layer 103, forming a first electrode layer 104 to be connected to the thin film transistor 1111, forming an organic insulating layer 1161 covering an end portion of the first electrode layer 104, forming a layer 105 containing an organic compound over the organic insulating layer 1161, and forming a second electrode layer 1162 over the layer 105 containing an organic compound and the organic insulating layer 1161, to separate an element 151 which has the layer containing an organic compound and a layer 1163 having the element 151 as shown in FIG. 23, there is a problem in that the separation occurs between the layer 105 containing an organic compound and the second electrode layer 1162. As a result, it is difficult to manufacture, with high yield, semiconductor devices in each of which the element which has the layer containing an organic compound is provided over a plastic substrate.
This is because the adhesion between the layer 105 containing an organic compound and the second electrode layer 106 is low. In specific, since polyimide, an epoxy resin, an acrylic resin, or the like that forms the organic insulating layer has a polar substituent such as an imide group, a cyano group, or a hydroxy group, the adhesion between the organic insulating layer and a layer formed with an inorganic compound, herein a gate insulating film or a first conductive layer, is high. However, since the layer 105 containing an organic compound functions as a semiconductor, the layer 105 containing an organic compound is formed by using a material having a carrier-transporting property. The material having a carrier-transporting property does not have a polar substituent in general. Accordingly, the adhesion between the layer 105 containing an organic compound and the second electrode layer 106 is so low that separation occurs between the layer 105 containing an organic compound and the second electrode layer 106 in a separation step.